The president must be doing something right. He's now getting advice (from all the wrong quarters) that he ought to stop standing up for the people, not the privileged. Of course, such arguments largely rest on pre-cast assumptions and self-serving calculations.

First out of the triangulating box was Clinton pollster Mark Penn, who wrote a remarkably data-free piece urging the president to draw back from dividing lines and retreat to formulaic centrism. In effect, Penn recommended a replay of the 1996 Clinton re-election campaign — when, in a pre-Monica time of rising prosperity and job growth, the incumbent still couldn't manage 50 percent of the popular vote, and was left without a serious mandate for his second term. It was this same approach, cautious and at times almost contentless, that doomed Hillary Clinton in the 2008 Democratic primaries. Voters were instead drawn to the cause and candidate of change. (She could have been that candidate, but it was too late when she finally embraced the populism Penn had disdained in the early contests.)

Fight on, Mr. President. You're renewing your voice and your vision, and America is beginning to hear you again as it did in 2008.

Now come the real Republicans to second and amplify Penn's message to Obama.

In a speech at the Heritage Foundation, the Medicare-shredding Rep. Paul Ryan (R-Wis.) denounced the president's "divisive message that pits one group against another" with "fear, envy, and the politics of division." Predictably, Ryan railed against "class warfare" — the tired phrase ritually trotted out from the right wing's Orwellian dictionary to smear any call for economic justice and tax fairness.

Ryan knows a thing or two about class warfare. His proposed budget, supported by almost every Republican in the House, would wage war against the poor, against the education and health care of the middle class, and against the security of seniors, with Medicare voucherized and recipients forced to pay an additional $6,000 a year. The wealthy, and this is no surprise, would benefit from huge tax cuts paid for by the sacrifices of everyone else. No wonder Ryan doesn't want the president to confront this by campaigning for ideals of equity and the interests of hard-working and out-of-work Americans.

No matter who emerges from the substandard ranks of GOP presidential candidates — the choice ranges narrowly from the inauthentic to the incredible — is Obama supposed to forswear telling the truth on tax plans that would cosset the comfortable and slam the vast majority, even as budget cuts shred everything from college aid to workplace safety? To Republicans, drawing the contrast is class warfare. Thus they revile Occupy Wall Street — because they're eager to roll back financial regulation and reopen the casino of unbridled Wall Street speculation.

The president increasingly seems to understand that the differences here must be stated and debated and resolved — that here is a fundamental dividing line in our politics and 2012 is the time for Americans to decide.

Ryan is at least transparent. New York Times columnist David Brooks, on the other hand, sounds agonized and genuinely disappointed as he mourns Obama's passage from compromising to fighting for progressive values. Of course, Brooks doesn't share those values; but as a mainstream conservative, appalled by his party's rush to the ideological edge, he's periodically hoped that Obama would hold fast to a post-partisan course. The president can hardly be faulted for not giving it a good try. He just wasn't prepared to betray core convictions — and even if he had been, the evidence suggests that the congressional Republicans — now busily voting against measures like the payroll tax holiday (which they originally proposed) — would have opposed Obama in any event.

Brooks argues that the president can't prevail as the candidate of "income redistribution" and "big government." But that's a straw man, a caricature of the case Obama is making. He's not offering paeans to government. He's fighting for Medicare and for the Social Security that Rick Perry calls a Ponzi scheme and Mitt Romney would privatize. Obama's not demanding income redistribution. Have we ever heard that phrase from him? He's simply asking the wealthy to pay their share.

Brooks selectively cites polling data showing that voters don't like big government or redistribution — abstractions which obscure the findings of survey after survey that Americans overwhelmingly agree with the president when the abstract becomes the concrete. In the latest New York Times poll, a decisive majority supports higher taxes on the highest incomes — by 65 percent to 30 percent. There is similar support for most elements of the Obama jobs bill — for example, over 60 percent favor federal action to save the jobs of police officers, firefighters, and teachers.

This reflects a perennial paradox of our politics: Doubtful and sometimes hostile to government, people honor and fiercely defend much of what it actually does. Indeed, the GOP is on the shakiest ground — and the president on the strongest — on Social Security and Medicare. That was the blunt message in an NBC/WSJ poll: "Republicans might want to talk about revamping" these programs but Americans say "hands off."

Brooks contends that instead of fighting such battles, Obama should "champion a Grand Bargain strategy." When he did just that this summer during the debt-ceiling fight, the Republicans wouldn't meet the president even a quarter of the way. And he wasn't going to surrender to a bargain that would go down in history as the Unfair Deal. As John Kennedy once observed, it's impossible to reach agreement with those who insist "what's mine is mine, and what's yours is negotiable."

There's an alternative route, Brooks suggests. The president should take a Grand Bargain to the country. He should be the one in favor of "entitlement reform" — a euphemism for cutting Medicare and Social Security. This would be both bad policy and unavailing; by its very nature, a Grand Bargain only succeeds when both sides work together as Ronald Reagan and Tip O'Neil did to save Social Security in 1983.

Elections are a moment of choosing — and some elections redefine the character of the nation and reset its direction for decades to come. And much as Brooks and many like him might prefer it, the fight can't be made, and for Obama certainly can't be won, on the pallid field of unrequited conciliation. Brooks complains that a real fight will be "viciously negative," presumably toward Mitt Romney. Why isn't Romney's record as a job-destroying take-over artist relevant? What's vicious here is how he made so much of his vast fortune. Why shouldn't he be judged by his patent lack of conviction? Conservatives are right to wonder what Romney believes in other than himself. And that's a negative he himself has created.

So fight on, Mr. President. You're renewing your voice and your vision, and America is beginning to hear you again as it did in 2008. Don't forget how FDR fought back in 1936 against the "forces of greed and privilege." Don't forget that in the late summer of 2000, Al Gore achieved a 16- to 22-point turnaround in the polls as he spoke the populism he truly felt, culminating in his acceptance address at the Democratic convention.

Brooks doesn't want you to "sound... a bit like Al Gore." I do. A populist appeal is not just your path to victory, but now, as it often was in the past, the path to a better, fairer, and more prosperous country for all Americans.

As long as you keep fighting, the critics will keep complaining. Every time they do, think of Harry Truman in 1948, written off, facing a "do-nothing Congress," assailed for class warfare, but clear in purpose and in principle. And think of what he promised as he came to the podium of a weary and worried Democratic convention: We "will win this election and make these Republicans like it — don't you forget that...The reason is the Democratic Party is the people's party, and the Republican Party is the party of special interest, and it always has been and always will be."

The Republicans didn't like it then. They won't like it now — and neither will the triangulators and a lot of the commentators. But in Truman's words, it's your time to "fight...for the ordinary people of this land and not...the favored classes or the powerful few."